Timing pulse generator



Sept. 1, 1970 F. H. BLITCHINGTON, JR. ETAL 9 TIMING PULSE GENERATORFiled Oct. 7, 1968 2 Sheets-Sheet l I|| I I I I /3 '1 I II l 36 f I f v/Z 597 6 0 l4 I l lll F. H HFlRR/S Sept. 1, 1970 F. H. BLITCHINGTON,JR.. ETAL 3,526,796

TIMING PULSE GENERATdR Filed Oct. 7, 1968 2 Sheets-Sheet 2 United StatesPatent 3,526,796 TIMING PULSE GENERATOR Frank Henning Blitchington, Jr.,Greensboro, and Richard Allen Harris, High Point, N.C., assignors toWestern Electric Company, Incorporated, New York, N.Y., a corporation ofNew York Continuation-impart of application Ser. No. 540,258,

Apr. 5, 1966. This application Oct. 7, 1968, Ser.

Int. Cl. H02k 17/42 US. Cl. 310-168 6 Claims ABSTRACT OF THE DISCLOSUREA substantially unipolar fast rise time pulse is produced when adiscontinuity in a magnetic coating on a non-magnetic base is moved pasta magnetic pickup head. A magnetic field established in the coatingalong the path of movement of the coating is interrupted by thediscontinuity to produce a localized field above the surface of thecoating to produce the pulse in the magnetic pickup.

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-partof our copending application Ser. No. 540,258, filed Apr. 5, 1966, nowabandoned.

FIELD OF THE INVENTION This invention relates to an apparatus forgenerating pulses, and in particular, to an apparatus for producingpulses in synchronism with the mechanical movement of a device. In manyarts, including the communications and information transmission arts,there is widespread use of timing pulses generated in synchronism withmechanical rotation of various devices. Examples of such devices aresignal samplers, information storage systems, automobile ignitionsystems, etc.

DESCRIPTION OF THE PRIOR ART In the prior art, the production of pulsesin synchronism with the rotation of a device is usually accomplished bymechanical operation of a switch by a cam or by wiping a contact on asegmented surface. In many applications, it is difllcult to obtain thedesired accuracy of operation. Also, the switch contacts are subject towear, corrosion and failure.

Several devices have been designed which utilize a change in theinductance of a magnetic circuit by the movement of a magnetic elementof the circuit. The change in inductance produces a pulse in a coilassociated with the magnetic circuit. The output pulses produced by suchdevices generally have slow rise times and do not have the accuracyrequired in many applications.

SUMMARY OF THE INVENTION Accordingly, an object of the present inventionis a new and improved apparatus for generating pulses.

Another object of this invention is an apparatus producing substantiallyunipolar fast rise time voltage pulses.

With these and other objects in view, the present invention contemplatesa magnetic material, having a discontinuity, on a non-magnetic basemoved past a magnetic pickup and wherein a magnetic field is establishedin the magnetic material in a direction along its direction of movementto produce a pulse when the discontinuity passes the magnetic pickup.One such device utilizes a magnetic drum wherein slots are formedthrough a magnetic material coated on the surface of the drum. Acircumferential magnetic field is established in the magnetic materialby the rotation of the drum adjacent to one pole of a magnet. The fieldadjacent to the discontinuity pro- 3,526,796 Patented Sept. 1, 1970duces a substantially unipolar fast rise time pulse when thediscontinuity passes the magnetic pickup.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a pulsegenerating apparatus embodying the principles of the invention.

FIG. 2 is a plan View particularly showing one theory of operation ofthe apparatus shown in FIG. 1.

FIG. 3 is a representation of the pulse-like voltage output of themagnetic pickup shown in FIGS. 1 and 2.

DETAILED DESCRIPTION Referring first to FIG. 1, there is shown anapparatus for generating pulse-like voltages. The apparatus includes asegmented drum 10, a magnet 11, and a magnetic pickup 12. The drum 10 isrotated in a selected direction, such as that shown by the arrow in FIG.I, by a motor 15 through a shaft 16. The motor 15 may be operated insynchronism with the driving means for cams of a mechanical signalsampler or any other rotating apparatus. The shaft 16 is mounted forrotation at its upper end on an electrically grounded bearing 21.

The segmented drum 10 is comprised of an inner cylinder 19 and segments20 of a coating or outer cylinder mounted on the inner cylinder 19. Theinner cylinder 19 is made of a non-magnetic material such as brass,aluminum, plastic, etc. The outer cylinder segments 20 are made of aferromagnetic material having a high retentivity. For example, thesegments 20 may be formed by machining grooves 22 through a layer ofcobalt-nickel alloy, electrolytically plated on a brass cylinder 19.Generally, any magnetic coating which is suitable for use in makingmagnetic memory drums would be suitable for use in the segments 20 ofthe pulse generator. The grooves 22 extend parallel to the major axis ofthe drum 10, and as shown in FIGS. 1 and 2, extend all the way throughthe magnetic coating to interrupt a circumferential magnetic paththrough the segments 20. The grooves 22 need not extend all the waythrough the magnetic coating forming the segments 20 but must besufliciently through the coating to substantially interrupt the magneticpath which a circumferential magnetic field would occupy in the segments20. The grooves 22 must be relatively narrow compared to the width ofthe segments 20.

The magnet 11 may be a permanent bar magnet or an electromagnet with anorth pole and a south pole. In the example to be hereinafter described,it is assumed that the north pole of the magnet 11 is positionedadjacent the grooves 22 and the segments 20 of the outer cylinder. Themagnet 11 may have many other forms and positions to produce similarresults.

The magnetic pickup 12 may be any magnetic pickup head capable ofsensing magnetic signals on a magnetic memory drum, magnetic tape, etc.One such pickup device has a horseshoe or an enclosed ferromagnetic core24 with a gap 24a. A winding 25 on the core 24 is connected to outputconductors 26. The gap 24a is positioned adjacent the segments 20 of theouter cylinder. Fluctuations in the magnetic field within the core 24are produced by changes in the magnetic field applied across the gap 24ato produce output signals on the conductors 26. A diode 13 and anamplifier 14 connect the pickup 12 to a utilization circuit, such as anelectronic switch, etc.

The pickup 12 and the magnet 11 are positioned relative to the drum 10such that a point on the circumference of the rotating drum 10 passesnext to both the pickup 12 and the magnet 11. The pickup 12 and themagnet 11 are positioned as close as possible to the drum 10 Withoutengaging the drum. The circumference of the drum 10 should be accuratelyformed to maintain uniform spacing between the pickup 12 and the druml0.

Referring now to FIG. 3, in assuming that the segmented drum is rotatedin a clockwise direction (as seen in FIG. 2) and that the north pole ofthe magnet 11 is positioned adjacent the drum 10, a voltage wave 27appears on the output conductors 26 of the magnetic pickup 12. Thepositive portion 28 of the voltage wave 27 has a peak magnitudeapproximately twenty times greater than the peak magnitude of thenegative portion 29. Assuming the time of the initiation of the positivepulse 28 and the terminal of the positive portion 29 to be one cycle,the positive portion 28 occupies approximately of the cycle. Moreover,it has been observed that the area within the positive and negativeportions 28 and 29 appear substantially equal in any one cycle.

The quality of the wave form or the sharpness in rise time in the pulse28 is dependent upon the relative velocity between the pickup 12 and thesegmented cylinder 20. At velocities below a predetermined low relativevelocity and above a predetermined high relative velocity the magnitudeand sharpness of the pulse 28 deteriorates. It is believed that theoperating characteristics of the magnetic pickup 12 and the variousparameters of the segmented drum 10 control the optimum range ofrotational velocities which produce satisfactory pulses 28.

The theory of operation of the present pulse generating apparatusappears to be that the movement of the segments 20 and grooves 22 pastthe magnet 11 orients and expands the magnetic domains in the segments20 to establish and maintain a magnetic field in a single rotarydirection through the segments. Since the circumferential path for themagnetic flux through the segments 20 is interrupted by thediscontinuities or grooves 22, the magnetic flux bulges outward at eachof the grooves 22 as shown in FIG. 2. Thus, when a groove 22 movesadjacent to the gap 24a of the pickup 12, the concentration of fluxbulging from the narrow groove 22 produces an abrupt increase inmagnetic field in the core 24, as shown in FIG. 2, to produce a sharpoutput pulse 28 on the leads 26. When the groove 22 moves away from thegap 24a, the field in the core 24 collapses and may even reverse toproduce the negative portion 29 of the signal 27 on the leads 26. Due tothe characteristics of the pickup 12 and its core 24, the collapsing ofthe magnetic field in the core 24 occurs at a much slower rate than therate of increase of magnetic field which occurs when the groove 22 isnext to the gap 24a. Adjacent the intermediate portions of each segment20, there will exist a weak magnetic field which has a polarity oppositeto the polarity of the field bulging from a groove 22. As shown by thephantom representation of a core 24' and a gap 24a in FIG. 2, this weakfield may produce a weak field in the core 24 which has a polarityopposite to the polarity of the field produced in the core 24 by thefield bulging from a groove 22. The rate of change of flux in the core24 due to the weak field adjacent the intermediate portions of thesegments 20 is much less than the rate of change in flux in the core 24due to the field bulging from the grooves 22.

While the apparatus described utilizes a segmented magnetic drum, it isbelieved that other segmented magnetic mediums would be suitable. Forexample, a flexible tape having closely spaced magnetic segments coatedthereon may be moved sequentially past a magnet and a magnetic pickup toproduce substantially unipolar fast rise time pulses.

There may be additional magnetic pickups, similar to pickup 12 locatedin the same circumferential path as the magnet 11 and pickup 12 toproduce pulses having the same or dilferent phases relative to thepulses produced by the pickup 12. Also, there may be additional pairs ofmagnets and pickup heads adjacent the drum 10 or other drums on theshaft 16.

EXAMPLE 1 In a device built in accordance with the above description,the inner cylinder 19 was made of brass and has a radius of .500 inch. A0.125 inch layer of cobaltnickel alloy was electrodeposited on thecircumference of the inner cylinder 19. Eighteen grooves 22 having awidth of approximately .031 inch and evenly spaced around thecircumference of the drum 10 were cut completely through thecobalt-nickel layer into the inner cylinder 19 to form the segments 20.The north pole of the magnet 11 and the magnetic pickup 12 werepositioned adjacent the drum approximately from each other.

When the drum 10 was rotated at 1200 r.p.m., the wave 27 depicted inFIG. 3 was observed on an oscilloscope connected to conductors 26 with360 pulses per second produced on leads 26. The magnitude of thepositive wave portions 28, in addition to bearing a 20 to l'ratio to thenegative wave portion magnitudes 29, were observed to exhibit unusuallyfast rise times. It was'found that at rotational velocities less than350 r.p.m. or greater than 4000 r.p.m., the 20 to 1 ratio of thepositive wave portion 28 to the negative wave portion 29 deteriorated.

Within the 350 to 4000 r.p.m. range, the areas within the positive andnegative wave portions 28 and 29 were observed to be approximatelyequal. Rotation of the drum 10 in the opposite direction reversed thepolarity of the Wave portions 28 and 29, depicted in FIG. 3, as didreversal of the polarity of the magnet 11. The diode 13 easilyeliminated the low magnitude, negative wave portion 29 so that only thehigh magnitude fast rise time positive wave portions 28 were applied tothe amplifier 14-.

EXAMPLE 2 In a second drum 10, the radius R of the inner cylinder 19 was1.000 inch and with the thickness of the layer forming the segments 20remaining at 0.125 inch..Thirtysix grooves were spaced evenly around thedrum 10. It was observed that the 20 to 1 ratio of the magnitude of thepositive wave portion 28 to the negative wave portion 29 occurred in arange of rotational velocity which was /2 of the critical velocity rangeof Example 1. That is, the 20 to 1 positive to negative magnitude ratiooccurred between the rotational velocity of r.p.m. and 2000 r.p.m.

It is to be understood that the above describedembodiments are simplyillustrative of the principles of the invention. Many other embodimentsmay be devised by those skilled in the art without departing from thescope and spirit of the invention.

What is claimed is:

1. An apparatus for generating fast rise time pulses comprising:

a non-magnetic base;

a plurality of segments of remanently magnetizable material mounted onthe base in a spaced relationship;

a magnetic pickup for producing a pulse in response to a change in amagnetic field applied thereto;

means for moving the base relative to the pickup such that the segmentsmove sequentiallyin a path adjacent to the pickup; and

means disposed in spaced relation to the pickup for establishing andmaintaining a remanent magnetic field in the segments in a uniformdirection parallel to the direction of movement of the base relative tothe pickup to produce fast rise time pulses in the magnetic pickup.

2. An apparatus for generating a fast rise'time pulse comprising:

a non-magnetic base having a surface;

a magnetic coating on the surface of the base capable of assuming astate of remanence and having a discontinuity;

means for moving the base such that the magnetic coating on the surfaceof the base moves in a path past a point;

a magnetic pickup located at the point for sensing changes in themagnetic field adjacent the magnetic coating; and

means disposed in spaced relation to the pickup for establishing aremanent magnetic field in the magnetic coating in a direction along thepath of movement to produce a fast rise time pulse in the pickup whenthe pickup senses the interruption of the magnetic field by thediscontinuity. 3. An apparatus for generating fast rise time pulsescomprising:

(a) a rotatable magnetic drum having a non-magnetic cylindrical core, amagnetic coating on the core capable of assuming a state of remanence;and a longitudinal slot formed substantially through the magneticcoating to interrup the continuity of a circumferential magnetic paththrough the magnetic coating; (b) a magnetic pickup head adjacent to thedrum; means for rotating the drum relative to the pickup head; and (d)means disposed in spaced relation to the pickup head for establishing acircumferential magnetic field in the magnetic coating such that a pulsehaving a fast rise time is produced by the pickup head When the slotpasses the pickup head. 4. An apparatus for generating substantiallyunipolar fast rise time pulses comprising:

(a) a rotatable magnetic drum having a non-magnetic cylindrical core, amagnetic coating on the core capable of assuming a state of remanence,and a plurality of longitudinal slots formed substantially through themagnetic coating to interrupt the continuity of a circumferentialmagnetic path through the magnetic coating;

(b) a magnetic pickup head adjacent to the drum;

(c) means for rotating the drum relative to the pickup head; and

(d) means disposed in spaced relation to the pickup head for producing amagnetic field which intersects the magnetic coating at a point in acircumferential path passing adjacent to the pickup head to producesubstantially unipolar pulses having fast times in the pickup head.

5. An apparatus as recited in claim 1, wherein the spaced distancesbetween adjacent segments of magnetic material are substantiallynarrower than the Width of individual ones of said segments along thedirection of movement of said base.

'6. An apparatus as recited in claim 4, wherein the distance betweenadjacent ones of said plurality of longitudinal slots is substantiallygreater than the Width of individual ones of said slots.

References Cited UNITED STATES PATENTS 1,659,729 2/1923 Gannett 3 l01682,516,178 7/1950 Bohannon 3l0155 2,669,669 2/1954 Spaulding 3l0l553,122,666 2/1964 Guiot 310l56 3,132,337 5/1964 Martin 310-170 MILTON O.HIRSHFIELD, Primary Examiner R. SKUDY, Assistant Examiner US. Cl. X.R.310-45,

